The proposed research is designed to provide important information on the cytological an biochemical bases of immune recognition and regulation in insects. Experiments are designed using specific enzyme assays, sensitive electrochemical methods and lectin binding specificities, to assess the roles of blood cells and hemolymph components in the synthesis and utilization of substrate(s), enzymes and various intermediate catecholamine derivatives that form protein-polyphenol complexes around metazoan parasites. The array of genetically variant enzyme mutants of Drosophila melanolgaster hosts, together with both susceptible and resistant strains of the wasp parasitoid Leptopilina heterotoma available for the proposed study provide exceptionally suitable experimental systems for investigating not only the cell-mediated immune response that is manifested by numerous insects, but also the mechanisms of parasite-induced suppression of host defenses.